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June 1991 LSAT
A fourteen–year study of finches on the Galapagos islands concluded that there is a definite relationship between cli...
on June 16 at 07:22PM
Could you please explain why B is the answer?
on June 27 at 02:16PM
Happy to help!
We are looking for the answer choice which outlines the assumption that is necessary for the passage to properly draw its conclusion. The correct answer choice will be the one that, when negated, no longer allows the conclusion to be drawn.
The passage tells us that a study of finches on the Galápagos Islands concluded that there is a definite relationship between climate and the population size of finch species which thrive there.
Drought - more members of larger species survive because their bills are big enough to crack large, hard seeds; smaller birds are not able to eat these seeds
Rain - fewer member of larger species survive because the rain supports the growth of plants which produce small seeds; some larger finches cannot keep up because they must consume so many small seeds to meet their energy demands
Answer choice (B) is correct because the negation of this assumption no longer allows the conclusion to be properly drawn. If rain does not necessarily result in fewer large, hard seeds being produced, then it doesn't make sense that the decrease in larger finches is due to the rain as they would still be able to eat the same amount of large, hard seeds.
The assumption allows the conclusion to be properly drawn as a decrease in the number of large, hard seeds would mean that the finches would be forced to eat the smaller seeds, resulting in the decrease in larger finches as outlined in the passage.
Hope this is helpful! Please let us know if you have any further questions.
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